Preparation of optically active 3-substituted piperidines via ring expansion: Synthesis of 4-amino- and 4-fluoro-1,4,5-trideoxy-1,5-imino-D-ribitol and 1,5-dideoxy-1,5-imino-D-ribitol

A new method for the preparation of optically active 3-substituted 1-benzylpiperidines based on the ring expansion of the 1-benzyl-2-(methylsulfonyloxymethyl)pyrrolidine 13 with various nucleophiles has been described. Synthesis of 4-amino-1,4,5-trideoxy-1,5-imino-D-ribitol 5, 1,4,5-trideoxy-4-fluoro-1,5-imino-D-ribitol 6 and 1,5-dideoxy-1,5-imino-D-ribitol 7 has also been achieved by a route which involves ring expansion of compound 13.